Heat exchanger unit

ABSTRACT

A heat exchanger unit includes at least two heat exchangers of the plate fin type that are substantially identical cuboids offset from each other. The heat exchangers are linked to at least one single distribution conduit and at least one single collection conduit. At least one first heat exchanger is situated on one side relative to the axis of the single distribution conduit and at least one second heat exchanger is situated on the other side relative to the axis of the single distribution conduit. A first face of the first heat exchanger is parallel to the nearest face of the second heat exchanger, but offset in the direction of the axis of the single distribution conduit. Each heat exchanger is fluidly connected to the face proximate to the distribution conduit, the offset being such that the each fluid connection does not contact one another.

The present invention concerns a heat exchanger unit and in particular a heat exchanger unit comprising at least two heat exchangers.

It is common to use an assembly of several identical heat exchangers to form a heat exchanger. A stream to be cooled is sent to all the heat exchangers via a distribution conduit and a plurality of conduits each send part of the stream to one of the heat exchangers. Similarly the cooled streams are removed from each of the heat exchangers by individual conduits, each of which is connected to a collection conduit which contains the cooled stream sent to the heat exchangers by the distribution conduit.

Such a heat exchanger unit is described in “The Interaction of Heat Transfer and Pressure Drop on Manifolding Aluminium Plate Fin Heat Exchangers” by Sotzek in Linde Reports on Science and Technology, 61/1999, in FR-A-2844040 and in WO-A-05/085728.

It is desired to make the heat exchanger unit as compact as possible, in particular by reducing the space the heat exchanger unit takes up at floor level (“footprint”). This can reduce or eliminate the need to make welded connections on site.

The heat exchangers A, B, C, D can be placed in a line as shown in FIG. 1 or else in a square format, exchangers A and C being on one side of the conduit and exchangers B and D on the other side (FIG. 2, conduit not shown).

In the configuration of FIG. 2, it is not possible to place the heat exchangers on either side of a collection conduit too closely together since, as the heat exchangers are identical, the fluid conduits connected to the adjacent faces on either side of the conduit are at the same position on the side wall of the heat exchangers and so prevent the heat exchangers from being placed close together.

One object of the present invention is a heat exchanger unit comprising at least two heat exchangers of the plate fin type, the heat exchangers being identical and having substantially the same dimensions and having the form of a cuboid, the heat exchangers being linked to at least one single distribution conduit and at least one single collection conduit, at least one first heat exchanger being situated on one side relative to the axis of the single distribution conduit and at least one second heat exchanger being situated on the other side relative to the axis of the single distribution conduit, a first face of the first heat exchanger being parallel to the nearest face of the second heat exchanger but offset in the direction of the axis of the single distribution conduit and each heat exchanger having a fluid connection conduit connected to the face proximate to the distribution conduit, the offset being such that the fluid connection conduits do not contact one another.

Additionally, optional features may exist, including

-   -   the single distribution conduit is linked to the first exchanger         via a first conduit running perpendicular to the single         distribution conduit and to the second exchanger via a second         conduit running perpendicular to the single distribution         conduit, the first conduit being linked to the single         distribution conduit at a first point and the second conduit         being linked to the single distribution conduit at a second         point, the first point being spaced from the second point along         the axis of the single distribution conduit.     -   the first conduit is linked to a header on the top or a side         wall of the first exchanger and the second conduit is linked to         the second exchanger at a point on top or the side wall of the         second heat exchanger.     -   the first face of the first heat exchanger is offset to the         nearest face of the second heat exchanger by an offset distance         less than the length of the face in the direction of the axis of         the distribution conduit.     -   the offset distance is less than half the length of the face in         the direction of the axis of the distribution conduit.     -   the offset distance is substantially equal to the diameter of         the first and/or second conduits.     -   the unit comprises at least four exchangers of the plate fin         type, at least two first exchangers being situated on one side         relative to the axis of the single distribution conduit and at         least two second exchangers being situated on the other side         relative to the axis of the single distribution conduit, each of         the first heat exchangers having a first face parallel to the         nearest face of one of the second heat exchangers but offset in         the direction of the axis of the single distribution conduit and         each heat exchanger having a fluid connection conduit connected         to the face proximate to the distribution conduit, the offset         being such that the fluid connection conduits do not contact one         another.     -   the single distribution conduit is linked to the third exchanger         via a third conduit running perpendicular to the single         distribution conduit and to the fourth exchanger via a fourth         conduit running perpendicular to the single distribution         conduit, the third conduit being linked to the single         distribution conduit at a third point and the second conduit         being linked to the single distribution conduit at a fourth         point, the third point being spaced from the fourth point along         the axis of the single distribution conduit and the third point         being spaced from the second point along the axis of the single         distribution conduit, the distance between the second and third         points being at least twice the distance between the first and         second points and at least twice the distance between the third         and fourth points.     -   each heat exchanger has a centre of gravity, the centre of         gravity of an exchanger on one side of the single distribution         conduit being offset along the axis of the single distribution         conduit for the centre of gravity of the nearest exchanger on         the other side of the single distribution conduit.     -   the fluid connection conduit connected to the first face of each         exchanger is connected to a point falling on a line         perpendicular to the axis of the distribution conduit which         divides the face into two equal halves.

According to a further aspect, there is provided a cold box including a heat exchanger unit as described above, the heat exchanger unit being surrounded by insulation.

According to a further aspect, there is provided a cryogenic air separation unit including a heat exchanger unit or a cold box as described above, the air separation unit including a distillation column system connected to the heat exchanger unit.

The invention will be described in greater detail with reference to FIGS. 3 and 5, which show a heat exchanger unit according to the invention, FIGS. 3 and 4 showing overhead views and FIG. 5 showing a side view.

The heat exchangers A, B, C and D are identical, having the same dimensions and the same connections. The exchanger B is disposed as a mirror image of exchanger A and exchanger D is a mirror image of exchanger C, the mirror image being slightly displaced along the axis of the conduit E. The conduit E (shown in dotted lines) runs between exchangers A, C and B, D and carries air to the heat exchangers. Each of the exchangers is disposed below the conduit E and has connections 5A, 5B, 5C, 5D to a conduit F (not shown), these connections only being shown in cross-section. Elements belonging to exchanger A are designated by the letter A after the numeral reference and so on.

The figure also shows connections 1A, 1B, 1C, 1D which connect to the faces of the heat exchangers running parallel to the axis of the conduit E and which are proximate thereto. In the specific embodiments, these connections are outlet conduit for warmed high pressure nitrogen but they could of course contain other fluids than high pressure nitrogen.

Because of the offset between the heat exchanger, the heat exchangers can be placed close together, without touching each other and without any of the connections 1A, 1B, 1C, 1D touching one another. In this way the heat exchangers A and C can be as close as possible to the exchangers B, D.

The heat exchangers also have connections 3A, 3B, 3C, 3D for the headers on the top of the heat exchangers, these connections permitting the removal of warmed gaseous oxygen from the heat exchangers.

FIG. 4 shows conduit E for low pressure gaseous nitrogen cooled in the heat exchangers A, B, C, D and removed from the heat exchangers to conduit E via the conduits 7A, 7B, 7C and 7D. It will be noted that the conduits are arranged in pairs extending perpendicular to the axis of conduit E. The conduit 7A is offset to conduit 7B because of the offset positions of exchangers A, B. The conduit 7C is offset to conduit 7D because of the offset positions of exchangers C, D. The offset between the heat exchangers is roughly equal to the diameter of one of the conduits 7A, 7B, 7C, 7D, which all have the same diameter.

In this particular case, the heat exchangers are used to cool air to be sent to a column system of a cryogenic distillation plant. The air is cooled in the heat exchangers by indirect heat exchange with fluids from the cryogenic distillation plant.

Each of the heat exchangers A, B, C, D is in the form of a cuboid comprising a plate fin heat exchanger made of aluminum, the cuboid being connected to headers to introduce and remove fluids therefrom. The plate fin heat exchanger comprises a series of plates spaced from one another by fins. The heat exchangers each have two conduits 5A, 5B, 5C, 5D connected to conduit F for the removal of waste oxygen. These pairs of conduits are positioned on both sides of the conduits 7A, 7B, 7C, 7D and are offset in the same way as these conduits.

Conduits 9A, 9B, 9C, 9D are air conduits. Conduit F is a conduit for high pressure gaseous nitrogen which receives warmed high pressure gaseous nitrogen from the four heat exchangers A to D. G is a gaseous oxygen stream from the subcooler.

FIG. 5 shows the entire heat exchanger unit, exchanger D being hidden by the others A, B, C and the entire unit being mounted on a support structure H. The same elements are shown as in FIG. 4 with the addition of conduits J, K, L, M. Conduit J is the conduit sending low pressure gaseous nitrogen from the air separation column system to the heat exchangers A, B, C, D. Conduit K is a waste oxygen conduit bringing waste oxygen from the air separation column system to the heat exchangers A, B, C, D. Conduit L is a gaseous oxygen conduit. Conduit M is a gaseous air conduit.

This allows the overall width of a heat exchanger unit to be reduced by around 400 mm, for a total width of 6000 mm. This means in some cases, that the heat exchanger unit can be transported as an assembled unit, rather than having to connect the heat exchangers together on site.

The heat exchanger unit is preferably surrounded by insulation and enclosed in an enclosure, called a cold box.

The heat exchanger unit may from part of cryogenic distillation unit, such as an air separation unit where it is used to cool the feed air to a cold enough temperature to allow it to be distilled.

It is obvious that the heat exchanger need only comprise two heat exchangers B and A or C and D at its simplest. 

1-13. (canceled)
 14. A heat exchanger unit comprising: a first heat exchanger; a second heat exchanger, wherein the first heat exchanger and the second heat exchanger are both of the plate fin type, wherein the first heat exchanger and the second exchanger have substantially the same dimensions and are in the form of a cuboid; a distribution conduit; and a collection conduit, wherein the first heat exchanger and the second heat exchanger are linked to the distribution conduit and the collection conduit, wherein the first heat exchanger is situated on one side relative to the axis of the distribution conduit and the second heat exchanger is situated on the other side relative to the axis of the distribution conduit, wherein a first face of the first heat exchanger being parallel to the nearest face of the second heat exchanger but offset in the direction of the axis of the distribution conduit and each heat exchanger having a fluid connection conduit connected to the face proximate to the distribution conduit, the offset being such that the fluid connection conduits do not contact one another.
 15. The heat exchanger unit of claim 14, wherein the distribution conduit is linked to the first heat exchanger via a first conduit running perpendicular to the distribution conduit and to the second exchanger via a second conduit running perpendicular to the distribution conduit, the first conduit being linked to the distribution conduit at a first point and the second conduit being linked to the distribution conduit at a second point, the first point being spaced from the second point along the axis of the distribution conduit.
 16. The heat exchanger unit as claimed in claim 14, wherein the first conduit is linked to a header on the top or a side wall of the first exchanger and the second conduit is linked to the second exchanger at a point on top or the side wall of the second heat exchanger.
 17. The heat exchanger unit as claimed in claim 14, wherein the first face of the first heat exchanger is offset to the nearest face of the second heat exchanger by an offset distance less than the length of the face in the direction of the axis of the distribution conduit.
 18. The heat exchanger unit as claimed in claim 17, wherein the offset distance is less than half the length of the face in the direction of the axis of the distribution conduit.
 19. The heat exchanger unit as claimed in claim 17, wherein the offset distance is substantially equal to the diameter of the first and/or second conduits.
 20. The heat exchanger unit as claimed in claim 14, comprising a third heat exchanger and a fourth heat exchanger, wherein the third heat exchanger is identical to the first heat exchanger and the fourth heat exchanger is identical to the second heat exchanger, wherein the third heat exchanger is situated on the same side of the distribution conduit as the first heat exchanger and the fourth heat exchanger is situated on the same side of the distribution conduit as the second heat exchanger, wherein the third heat exchanger has a first face parallel to a proximate face of the fourth heat exchanger but offset in the direction of the axis of the distribution conduit and each heat exchanger having a fluid connection conduit connected to the face proximate to the distribution conduit, the offset being such that the fluid connection conduits do not contact one another.
 21. The heat exchanger unit as claimed in claim 20, wherein the distribution conduit is linked to the third heat exchanger via a third conduit running perpendicular to the distribution conduit and to the fourth exchanger via a fourth conduit running perpendicular to the distribution conduit, the third conduit being linked to the distribution conduit at a third point and the fourth conduit being linked to the distribution conduit at a fourth point, the third point being spaced from the fourth point along the axis of the single distribution conduit and the third point being spaced from the second point along the axis of the single distribution conduit, the distance between the second and third points being at least twice the distance between the first and second points and at least twice the distance between the third and fourth points.
 22. The heat exchanger unit as claimed in claim 14, wherein each heat exchanger has a centre of gravity, the center of gravity of the first heat exchanger being offset along the axis of the distribution conduit by the center of gravity of the second heat exchanger.
 23. The heat exchanger as claimed in claim 14, wherein the fluid connection conduit connected to the first face of each exchanger is connected to a point falling on a line perpendicular to the axis of the distribution conduit which divides the face into two equal halves.
 24. The heat exchanger unit as claimed in claim 14, wherein the heat exchanger unit is disposed within a cold box and the heat exchanger unit is surrounded by insulation.
 25. The heat exchanger unit as claimed in claim 14, wherein the heat exchanger unit is part of a cryogenic air separation unit further comprising a cold box and a distillation column system, wherein the distillation column system is in fluid communication with the heat exchanger unit.
 26. A heat exchanger unit comprising at least two heat exchangers (A, B, C, D) of the plate fin type, the heat exchangers being identical and having substantially the same dimensions and having the form of a cuboid, the heat exchangers being linked to at least one single distribution conduit (E, F) and at least one single collection conduit (J, K), at least one first heat exchanger (A, C) being situated on one side relative to the axis of the single distribution conduit and at least one second heat exchanger (B, D) being situated on the other side relative to the axis of the single distribution conduit, a first face of the first heat exchanger being parallel to the nearest face of the second heat exchanger but offset in the direction of the axis of the single distribution conduit and each heat exchanger having a fluid connection conduit (1A, 1B, 1C, 1D) connected to the face proximate to the distribution conduit, the offset being such that the fluid connection conduits do not contact one another.
 27. The heat exchanger unit as claimed in claim 26, wherein the single distribution conduit (E) is linked to the first exchanger (A, C) via a first conduit (7A, 7C, 9A, 9C) running perpendicular to the single distribution conduit and to the second exchanger (B, D) via a second conduit (7B, 7D, 9B, 9D) running perpendicular to the single distribution conduit, the first conduit being linked to the single distribution conduit at a first point and the second conduit being linked to the single distribution conduit at a second point, the first point being spaced from the second point along the axis of the single distribution conduit.
 28. The heat exchanger unit as claimed in claim 26, wherein the first conduit (7A, 7C, 9A, 9C) is linked to a header on the top or a side wall of the first exchanger and the second conduit (7B, 7D, 9B, 9D) is linked to the second exchanger at a point on top or the side wall of the second heat exchanger.
 29. The heat exchanger unit as claimed in claim 26, wherein the first face of the first heat exchanger is offset to the nearest face of the second heat exchanger by an offset distance less than the length of the face in the direction of the axis of the distribution conduit.
 30. The heat exchanger unit as claimed in claim 29, wherein the offset distance is less than half the length of the face in the direction of the axis of the distribution conduit.
 31. The heat exchanger unit as claimed in claim 30, wherein the offset distance is substantially equal to the diameter of the first and/or second conduits (7A, 7C, 7B, 7D, 9A, 9C, 9B, 9D).
 32. The heat exchanger unit as claimed in claim 26, comprising at least four exchangers (A, B, C, D) of the plate fin type, at least two first exchangers (A, C) being situated on one side relative to the axis of the single distribution conduit and at least two second exchangers (B; D) being situated on the other side relative to the axis of the single distribution conduit, each of the first heat exchangers having a first face parallel to the nearest face of one of the second heat exchangers but offset in the direction of the axis of the single distribution conduit and each heat exchanger having a fluid connection conduit connected to the face proximate to the distribution conduit, the offset being such that the fluid connection conduits do not contact one another.
 33. The heat exchanger unit as claimed in claim 26, wherein each heat exchanger (A, B, C, D) has a centre of gravity, the centre of gravity of an exchanger (A) on one side of the single distribution conduit being offset along the axis of the single distribution conduit for the centre of gravity of the nearest exchanger (B) on the other side of the single distribution conduit. 